EXPERIMENTAL CONTROL OF CERTAIN REGU 



LATORY PROCESSES IN HARENACTIS 



ATTENUATA. 



C. M. CHILD. 



In my study of form regulation in Cerianthus 1 it was shown 

 that distension of the enteron with fluid was an important factor 

 in regulation in this form. More recent work on Harenactis 

 attenuata an actinian inhabiting the tide flats near San Diego, 

 Cal., 2 has confirmed my earlier conclusions and has afforded cer- 

 tain striking examples of the importance of distension for the per- 

 sistence of parts. The results of my work on Harenactis will be 

 presented elsewhere, but it seems desirable to give a brief account 

 of certain experiments at this time since they illustrate so clearly 

 not only the importance of distension but the possibility of ex- 

 perimental control of the course of regulation. 



These experiments are concerned with the production of partial 

 discs proximal to the original disc in consequence of cuts part 

 way through the body. In my earlier experiments of this kind 

 on Cerianthus 3 it was found that in all cases the region directly 

 distal to the partial disc underwent atrophy and disappeared and 

 the partial disc gradually migrated toward the distal end of the 

 body and finally took the place of the atrophied portion. I 

 pointed out that the atrophy in these cases was very evidently 

 due to insufficient distension or absence of distension in the part 

 concerned and showed that the method of closure of the wound 

 in such cases resulted in isolation of the enteric cavity of the 

 atrophying region both from the exterior and from other portions 

 of the enteron. Although the entrance of water through the 

 wall of the body is apparently possible to a greater or less ex- 



1 Child, " Form Regulation in Cerianthus,'" I. -IX., BiOL. BULL., Vols. V.-VIII., 



I903-5- 



2 Child, "Form Regulation of Harenactis attenuata in Altered Environment," 



BIOL. BULL., Vol. XVI., No. i, 1908. 



3 Child, " Form Regulation in Cerianthus, VIII., Supplementary Partial Discs and 

 Heteroruorphic Tentacles," BIOL. BULL., Vol. VIII., No. 2, 1905. 



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